Method for manufacturing at least one portion of a box structure of an aircraft comprising a forming step, and a central wingbox thus obtained

ABSTRACT

A method for manufacturing at least a portion of a box structure obtained from an outer skin and a plurality of sections each having a joining face in contact with the outer skin. The method comprises a step of positioning the sections on a mold, a step of obtaining a flat fiber preform having a thickness substantially equal to the outer skin, a step of placing a central portion of the fiber preform on the sections positioned on a first face of the mold and a step of forming a lateral extension of the fiber preform to press the fiber preform against a forming surface. A central wingbox obtained by the method is provided and a forming tool for carrying out the method.

CROSS-REFERENCES TO RELATED APPLICATIONS

This application claims the benefit of the French patent application No.2201536 filed on Feb. 22, 2022, the entire disclosures of which areincorporated herein by way of reference.

FIELD OF THE INVENTION

The present application relates to a method for manufacturing at leastone portion of an aircraft box structure including a forming step and toa central wingbox thus obtained.

BACKGROUND OF THE INVENTION

As shown in FIG. 1 , an aircraft includes a fuselage 10, wings 12, and acentral wingbox 14 connecting the wings 12 and the fuselage 10.According to one embodiment shown in FIG. 2 , the central wingbox 14includes a top panel 16, a bottom panel 18, a front spar 20, and a rearspar 22.

The top and bottom panels 16, 18, as well as the front and rear spars20, 22, each have an internal face (oriented towards the center of thecentral wingbox), referenced respectively 161, 181, 201 and 221, thatare reinforced by stiffening members 24 on the internal faces thereof.

As shown in FIG. 3 , the central wingbox 14 is obtained from a pluralityof U- or C-shaped sections 26, 28 made of composite material, and anouter skin 30 of fiber reinforcements attached to the sections 26, 28.The plurality of U- or C-shaped sections 26, 28 are positioned about amold 32 (visible in FIG. 2 as a dot-and-dash line and partially in FIG.3 ).

The mold 32 has four faces 32.1 to 32.4 connected in pairs at the fouredges 32.A1 to 32.A4, shaped in the same manner as the internal faces161, 181, 201 and 221 of the top and bottom panels 16, 18 and the frontand rear spars 20, 22 of the central wingbox 14. According to onelayout, the mold 32 has a pivot axis A32, parallel to the edges 32.A1 to32.A4, to allow the fiber reinforcements to be wound.

The mold 32 includes slots 34 that are formed parallel to the edges32.A1 to 32.A4 in the faces 32.1 to 32.4 of the mold 32, with one slot34 for each stiffening member 24.

A method for manufacturing a central wingbox 14 comprises a step ofobtaining sections 26, 28, a step of positioning the sections 26, 28 onthe mold 32, a step of obtaining the outer skin 30 by winding fiberreinforcements about the mold 32, a step of applying a polymerizationcovering, a polymerization step, and a demolding step.

The step of obtaining the outer skin 30 by winding fiber reinforcementsis relatively long and has a significant impact on the cost of producingthe central wingbox 14.

Document WO2008020158 also proposes a method for manufacturing a centralwingbox.

According to a first embodiment illustrated in FIGS. 1 to 3 , thecentral wingbox is made by assembling four parts. According to thisfirst embodiment, to obtain a stiffened panel, a tool comprises a mainmold with hollow shapes designed to receive secondary molds in which T-or L-shaped fiber sections are positioned. Once the secondary moldscontaining the fiber sections have been positioned on the main mold, theouter skin is obtained by placing a flat preform on the main mold.Finally, the flat preform is covered with a counter-mold designed topress the flat preform against the main mold during a polymerizationstep. According to one layout, the stiffened panel comprises two flangesfolded to 90° on both sides of the central portion thereof provided withstiffening members. According to this layout, the main mold has twoflanks shaped like the flanges of the stiffened panel to be obtained andthe counter-mold is U-shaped to deform the flat preform so that the flatpreform matches the shapes of the main mold. This first embodiment isnot satisfactory because, since the central portion of the preform isnot held when the flanges thereof are folded, it is not possible to usethis first embodiment to obtain a stiffened panel with a single flange.

According to a second embodiment shown in FIG. 6 , to obtain acontinuous outer skin, the tool comprises a main mold comprising fourfaces provided with hollow shapes designed to receive secondary molds inwhich fiber sections are positioned. After the secondary moldscontaining the fiber sections have been placed on the main mold, theouter skin is obtained by winding fiber reinforcements about the mainmold. Even if this second embodiment obviates the assembly steps, it isnot satisfactory since, as indicated above, this fiber reinforcementwinding step is relatively long and has a significant impact on thecosts of producing the central wingbox.

The present invention is intended to overcome some or all of thedrawbacks in the prior art.

SUMMARY OF THE INVENTION

For this purpose, the invention relates to a method for manufacturing atleast one portion of a box structure comprising at least one stiffenedmain wall extended by at least one flange and/or by at least onestiffened secondary wall, the portion of the box structure beingobtained from an outer skin made of a composite material and from aplurality of sections made of a composite material, each having ajoining face in contact with the outer skin, the method comprising astep of obtaining the sections, a step of positioning the sections on amold comprising at least a first face on which the sections arepositioned, a step of obtaining a flat fiber preform having a thicknesssubstantially equal to the outer skin, a step of placing a centralportion of the fiber preform on the sections positioned on the firstface of the mold, the fiber preform having at least one lateralextension extending the central portion, a step of forming the lateralextension, a step of applying at least one polymerization covering, atleast one polymerization step, and at least one demolding step.

According to the invention, during the forming step, the main portion isheld against the joining faces of the sections positioned on the firstface of the mold by a main jaw. Additionally, the lateral extension ofthe fiber preform is folded against a forming surface, substantiallyperpendicular to the first face of the mold, by at least one secondaryjaw designed to move in translation parallel to the forming surface.

The fact that the outer skin is made from a flat fiber preform that isthen deformed in a forming step reduces production costs and increasesproduction rates. According to another advantage, the method accordingto the invention can provide stiffened panels with a single flange or asingle stiffened secondary wall. The method according to the inventionalso optimizes the contact between the joining faces of the sections andthe fiber preform.

According to another feature, during the forming step, the lateralextension of the fiber preform is held between a pair of secondary jawsdesigned to move in translation in at least one direction parallel tothe forming surface.

According to another feature, the fiber preform includes right- andleft-hand lateral extensions positioned on both sides of the mainportion.

According to another feature, the forming surface corresponds to joiningfaces of sections positioned on a side face of the mold.

The invention also relates to a method for manufacturing a centralwingbox comprising a top panel, a bottom panel, a front spar and a rearspar, characterized in that the central wingbox comprises:

a first portion comprising the top panel, the front and rear spars, andthe first and second flanges, the first flange being connected to thefront spar, approximately perpendicular to the front spar and extendingthe front spar in the direction opposite the rear spar, the secondflange being connected to the rear spar, approximately perpendicular tothe rear spar and extending the rear spar in the direction opposite thefront spar, the first portion being obtained using the method having oneof the aforementioned features,

a second portion comprising a stiffened panel shaped like the bottompanel and including first and second extensions arranged on both sidesof the bottom panel, the first extension being connected to the firstflange, the second extension being connected to the second flange.

The invention also relates to a central wingbox obtained using themanufacturing method and a forming tool to manufacture at least oneportion of a box structure comprising at least one stiffened main wallextended by at least one flange and/or by at least one stiffenedsecondary wall. This tool is characterized in that it comprises:

a mold having at least a first face shaped like the stiffened main walland designed to bear sections,

at least one main jaw comprising a contact face substantially parallelto the first face of the mold, designed to hold a main portion of afiber preform pressed against sections positioned on the first face ofthe mold,

at least one secondary jaw designed to fold a lateral extension of thefiber preform against a forming surface and to move in at least onedirection parallel to the forming surface.

According to another feature, the forming tool comprises at least onepair of upstream and downstream secondary jaws each designed to hold alateral extension of the fiber preform and to move in the directionparallel to the forming surface.

According to another feature, each upstream and downstream secondary jawcomprises a first contact face, the first contact faces of the upstreamand downstream secondary jaws being designed to be arranged on bothsides of the fiber preform, substantially parallel to each other foreach pair and perpendicular to a face of the mold against which thelateral extension held by the upstream and downstream secondary jaws isto be positioned.

According to another feature, each upstream secondary jaw comprises asecond contact face oriented towards the mold, substantially parallel tothe face of the mold against which the lateral extension held by theupstream and downstream secondary jaws is to be positioned, in operationthe second contact face being spaced apart from the sections positionedon the face of the mold by a distance substantially equal to thethickness of the fiber preform.

According to another feature, each downstream secondary jaw has at leastone moving belt on the first contact face thereof.

According to another feature, each upstream secondary jaw has at leastone moving belt on the first and/or second contact face thereof.

According to another feature, each upstream secondary jaw has a movingbelt stretched between at least three pivoting rollers arranged suchthat the moving belt moves on the first and second contact faces.

According to another feature, the tool comprises a first pair ofsecondary jaws designed to cooperate with a right-hand lateral extensionof the fiber preform and a second pair of secondary jaws designed tocooperate with a left-hand lateral extension of the fiber preform.

BRIEF DESCRIPTION OF THE DRAWINGS

Other features and advantages are set out in the description of theinvention below, given purely by way of example and with reference tothe attached drawings, in which:

FIG. 1 is a perspective view of an aircraft,

FIG. 2 is a perspective view of a central wingbox and a mold showing oneembodiment according to the prior art,

FIG. 3 is a longitudinal cross section of the central wingbox shown inFIG. 2 ,

FIG. 4 is a schematic view of a central wingbox showing an embodiment ofthe invention,

FIG. 5 is a schematic view of the different steps for positioning anouter skin showing one embodiment of the invention,

FIG. 6 is a schematic view of the different steps for positioning anouter skin showing another embodiment of the invention,

FIG. 7 is a schematic view of the different steps for positioning anouter skin showing another embodiment of the invention,

FIG. 8 is a schematic view of the different steps for positioning anouter skin showing another embodiment of the invention,

FIG. 9 shows a cross section of a stiffened panel obtained according tothe embodiment shown in FIG. 8 ,

FIG. 10 is a schematic view of the different steps for positioning anouter skin showing another embodiment of the invention,

FIG. 11 shows a cross section of a stiffened panel obtained according tothe embodiment shown in FIG. 10 .

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

According to one embodiment shown in FIG. 4 , a central wingbox 40includes a top panel 42, a bottom panel 44, a front spar 46, and a rearspar 48.

The top and bottom panels 42, 44 and the front and rear spars 46, 48have internal faces (oriented towards the center of the central wingbox)referenced respectively 421, 441, 461 and 481.

At least one of the top and bottom panels 42, 44 and the front and rearspars 46, 48 has at least one stiffening member 50, positioned on theinternal face 421, 441, 461, 481 thereof. According to one layout, eachof the top and bottom panels 42, 44 and each of the front and rear spars46, 48 has at least one stiffening member 50 on the internal face 421,441, 461, 481 thereof, and usually a plurality of stiffening members 50parallel to each other and oriented in a transverse direction.

The central wingbox 40 is made of composite material.

According to one embodiment, the central wingbox 40 is obtained from aplurality of sections 52, 54 made of composite material, such asU-shaped sections 52, C-shaped sections 54, or L-shaped sections, forexample. As shown in FIG. 5 , each U-shaped section has a base 52.1 andtwo flanges 52.2, 52.3 parallel to each other and positioned on bothsides of the base 52.1. Each C-shaped section comprises a V-shaped base54.1 and two flanges 54.2, 54.3 positioned on both sides of the V-shapedbase 54.1. The C-shaped sections 54 are positioned at the joining zonesof the top/bottom panels 42, 44 and the front/rear spars 46, 48. TheU-shaped sections 52 are inserted between the C-shaped sections 54.

According to one layout, each section 52, 54 is obtained from apre-impregnated fiber preform that may be partially polymerized topreserve the shape thereof.

According to one procedure, the sections 52, 54 are directly attached toat least one mold 56 that has one seat 58, such as a slot, for example,for each stiffening member 50. With U-, C- or L-shaped sections, eachseat 58 is designed to receive two adjoining flanges of two juxtaposedU-shaped sections 52 and/or C-shaped sections 54 and/or L-shapedsections.

Alternatively, the sections 52, 54 are positioned on secondary moldsattached to the mold 56.

The sections 52, 54 are not described in greater detail as the sectionscan be identical to the sections in the prior art. Naturally, thesections 52, 54 are not limited to a U-, C- or L-shaped cross section,but can have a T-, I-, L- or other cross section. Regardless of theembodiment, a section 52, 54 is made of a composite material andcomprises at least one joining face F52, F54 that is exposed when thesection 52, 54 is attached, directly or indirectly, to the mold 56.

In addition to the sections 52, 54, the central wingbox 40 comprises anouter skin 60 made of composite material, in contact with the joiningfaces F52, F54 of the sections 52, 54, as shown in FIG. 4 .

According to a first embodiment, the central wingbox 40 comprises firstand second assembled portions 62, 64, as shown in FIG. 4 . According toone layout, the first portion 62 comprises the top panel 42, the frontand rear spars 46, 48, and the first and second flanges 66.1, 66.2, thefirst flange 66.1 being connected to the front spar 46, approximatelyperpendicular to the front spar 46 and extending the front spar in thedirection opposite the rear spar 48, the second flange 66.2 beingconnected to the rear spar 48, approximately perpendicular to the rearspar 48 and extending the rear spar in the direction opposite the frontspar 46. Thus, the first portion 62 has an approximately omega-shapedcross section in a longitudinal plane.

The second portion 64 includes the bottom panel 44 and first and secondextensions 68.1, 68.2 that are arranged on both sides of the bottompanel 44 and that are substantially coplanar with the bottom panel 44.

The first and second portions 62, 64 are assembled by pressing the firstflange 66.1 against the first extension 68.1 and the second flange 66.2against the second extension 68.2, the first and second portions 62, 64being connected by gluing, by copolymerization, by linking elements suchas rivets or bolts for example, or by any other assembly technique.

According to this first embodiment, the mold 56 comprises a top face70.1 shaped like the internal face 421 of the top panel 42, a first sideface 70.2 shaped like the internal face 461 of the front spar 46 and asecond side face 70.3, opposite the second side face 70.2, shaped likethe internal face 481 of the rear spar 48. The top face 70.1 and thefirst and second side faces 70.2, 70.3 are designed to receive thesections 52, 54. According to one layout, the faces have seats 58 forreceiving the flanges 52.2, 52.3, 54.2, 54.3 of the U-shaped sections52, the C-shaped sections 54 or the L-shaped sections to form thestiffening members 50.

A method for manufacturing a central wingbox 40 comprises a step ofobtaining sections 52, 54, a step of positioning the sections 52, 54 onthe mold 56, a step of obtaining a flat fiber preform 72 having athickness substantially equal to the outer skin 60, a step of placingthe flat fiber preform 72 on the joining faces F52, F54 of the sections52, 54 positioned on the top face 70.1 of the mold 56, a step of formingthe flat fiber preform 72 in order to press the preform against thejoining faces F52, F54 of the sections 52, 54 positioned on the firstand second side faces 70.2, 70.3 of the mold 56, a step of applying atleast one polymerization covering, a polymerization step, and ademolding step. The flat fiber preform 72 is dimensioned to form theouter skin 60 of the top panel 42, the front/rear spars 46, 48, and thefirst and second flanges 66.1, 66.2. Thus, the flat fiber preform 72comprises a main portion 74 intended to be positioned on the top face70.1 of the mold 56 as well as right- and left-hand lateral extensions76.1, 76.2 that are located on both sides of the main portion 74 andthat are intended to be positioned on the first and second side faces70.2, 70.3 of the mold 56 and to form the first and second flanges 66.1,66.2. Each right- and left-hand lateral extension 76.1, 76.2 extendsbetween a first edge connected to the main portion 74 and a second freeedge.

During the forming step, the right- and left-hand lateral extensions76.1, 76.2 of the fiber preform 72 are simultaneously and equallypressed against the joining faces F52, F54 of the sections 52, 54positioned on the first and second side faces 70.2, 70.3 of the mold 56in order to balance the forces on both sides of the main portion 74 ofthe fiber preform 72.

According to the first embodiment, the second portion 64 comprises astiffened panel shaped like the bottom panel 44, having first and secondextensions 68.1, 68.2.

According to another embodiment shown in FIG. 7 , the mold 56 comprisesa top face 70.1 shaped like the internal face 421 of the top panel 42, afirst side face 70.2 shaped like the internal face 461 of the front spar46, a second side face 70.3 shaped like the internal face 481 of therear spar 48, and a bottom face 70.4 shaped like the internal face 441of the bottom panel 44. The top and bottom faces 70.1, 70.4 and thefirst and second side faces 70.2, 70.3 are designed to receive thesections 52, 54. According to one layout, the faces have slots 58 forreceiving the flanges 52.2, 52.3, 54.2, 54.3 of the U-shaped sections52, the C-shaped sections 54 or the L-shaped sections to form thestiffening members 50.

A method for manufacturing a central wingbox 40 comprises a step ofobtaining sections 52, 54, a step of positioning the sections 52, 54 onthe mold 56, a step of obtaining a flat fiber preform 72′ having athickness substantially equal to the outer skin 60, a step of placingthe flat preform 72′ on the joining faces F52, F54 of the sections 52,54 positioned on the top face 70.1 of the mold 56, a step of forming theflat fiber preform 72′ in order to press the preform against the joiningfaces F52, F54 of the sections 52, 54 positioned on the first and secondside faces 70.2, 70.3 then against the joining faces F52, F54 of thesections 52, 54 positioned on the bottom face 70.4 of the mold 56, astep of applying at least one polymerization covering, a polymerizationstep, and a demolding step. The flat fiber preform 72′ is dimensioned toform the outer skin 60 of the top and bottom panels 42, 44 and the frontand rear spars 46, 48. Thus, the flat fiber preform 72′ comprises a mainportion 74 intended to be positioned on the top face 70.1 of the mold 56as well as right- and left-hand lateral extensions 76.1, 76.2 that arelocated on both sides of the main portion 74 and that are intended to bepositioned on the first and second side faces 70.2, 70.3 and on thebottom face 70.4 of the mold 56. During the forming step, the right- andleft-hand lateral extensions 76.1, 76.2 of the fiber preform 72′ aresimultaneously and equally pressed against the joining faces F52, F54 ofthe sections 52, 54 positioned on the first and second side faces 70.2,70.3 then against the faces of the sections 52, 54 positioned on thebottom face 70.4 of the mold 56 in order to balance the forces on bothsides of the main portion 74 of the fiber preform 72′.

Regardless of the embodiment, the mold 56 has at least first and secondfaces, approximately forming a right angle, shaped like the internalfaces of an adjoining top or bottom panel 42, 44 and an adjoining frontor rear spar 46, 48.

Additionally, the method for manufacturing a central wingbox 40comprises a step of obtaining sections 52, 54, a step of positioning thesections 52, 54 on the mold 56 having at least first and second faces70.1, 70.2, 70.3 on which the sections 52, 54 are positioned, a step ofobtaining a flat fiber preform 72, 72′ having a thickness substantiallyequal to the outer skin 60, a step of placing the fiber preform 72, 72′on the sections 52, 54 positioned on the first face of the mold 56, astep of forming the fiber preform 72, 72′ in order to press the preformagainst the sections 52, 54 positioned on at least the second face ofthe mold 56, a step of applying at least one polymerization covering, atleast one polymerization step, and at least one demolding step. Thus,the fiber preform 72, 72′ includes a main portion 74 designed to bepositioned on the first face of the mold 56 and at least one lateralextension 76.1, 76.2 designed to be positioned at least on the secondface of the mold 56.

Regardless of the embodiment, the fiber preform 72, 72′ is made usingflat preform techniques such as fiber ply draping. These techniquesenable preforms to be obtained quickly and at a much lower productioncost than a winding technique.

According to one layout, the fiber preform 72, 72′ comprises a mainportion 74 and two lateral extensions 76.1, 76.2, positioned on bothsides of the main portion 74, that are simultaneously and equallypressed against the sections 52, 54 positioned on at least two opposingfaces of the mold 56. This layout balances the forces on both sides ofthe main portion 74 during the forming step.

According to a first procedure, the fiber preform 72, 72′ is foldedalong at least one fold line corresponding to an edge connecting a topor bottom panel 42, 44 and a front or rear spar 46, 48 during theforming step.

According to another procedure shown in FIGS. 5 to 7 , each lateralextension 76.1, 76.2 is gradually pressed against the sections 52, 54positioned on at least one face of the mold 56, starting from the firstedge of the lateral extension 76.1, 76.2 towards the second free edgethereof. This solution ensures that each lateral extension 76.1, 76.2 isin good contact with the sections 52, 54.

The manufacturing method described above is more specifically suited tomanufacturing the first portion 62 of the central wingbox 40 shown inFIG. 4 . Alternatively, the manufacturing method shown in FIG. 7 can beused to obtain a central wingbox without assembly.

Although described in relation to a central wingbox, the manufacturingmethod could be used to manufacture other box structures, such as awingbox, for example.

To implement the forming step, a forming tool comprises, in addition tothe mold 56, at least one main jaw 78 designed to press the main portion74 of the fiber preform 72, 72′ against the sections 52, 54 positionedon a first face of the mold 56, in particular the top face 70.1 thereof,and at least one pair of secondary jaws for each lateral extensiondesigned to hold the lateral extension 76.1, 76.2 of the fiber preform72, 72′ and to move in at least one direction parallel to the secondface of the mold.

According to one layout, the forming tool comprises a first pair ofsecondary jaws 80.1, 82.1 designed to cooperate with the right-handlateral extension 76.1 and a second pair of secondary jaws 80.2, 82.2designed to cooperate with the left-hand lateral extension 76.2.

The main jaw 78 includes a contact face F78 substantially parallel tothe first face 70.1 of the mold 56. The main jaw 78 is designed tooccupy a first position in which the main jaw 78 is withdrawn from themold 56 so as to enable placement of the fiber preform 72, 72′ and asecond position in which the main jaw 78 is moved towards the mold 56 soas to keep the perform pressed against the sections 52, 54 positioned onthe first face of the mold 56.

According to one embodiment shown in FIG. 6 , the forming tool includesa structure 84 and at least a first joint 86 connecting the main jaw 78and the structure 84 that is designed to allow the main jaw 78 to movebetween the first position and the second position. The first joint 86may for example be a sliding link.

Each secondary jaw 80.1, 82.1, 80.2, 82.2 has a first contact faceF80.1, F82.1, F80.2, F82.2. These first contact faces of the secondaryjaws are substantially parallel to each other in each pair,perpendicular to the second or third side face 70.2, 70.3 of the mold56, and designed to be arranged on both sides of the fiber preform 72,72′. For each pair, at least one of the two secondary jaws 80.1, 82.1,80.2, 82.2 is movable in a direction perpendicular to the first contactfaces F80.1, F82.1, F80.2, F82.2 between a first position in which thetwo secondary jaws 80.1, 82.1, 80.2, 82.2 are withdrawn from each otherso as to allow the fiber preform 72, 72′ to be placed between the twosecondary jaws 80.1, 82.1, 80.2, 82.2 and a second position in which thetwo secondary jaws 80.1, 82.1, 80.2, 82.2 are brought together and thefirst contact faces F80.1, F82.1, F80.2, F82.2 of the two secondary jaws80.1, 82.1, 80.2, 82.2 are in contact with and hold the fiber preform72, 72′.

According to one embodiment, the forming tool comprises, for each pairof secondary jaws 80.1, 82.1, 80.2, 82.2, a support 88 and at least onesecond joint 90 that connects the support 88 and one of the secondaryjaws 80.1, 82.1, 80.2, 82.2 and is designed to allow the secondary jawsto move between the first position and the second position. The secondjoint 90 may for example be a sliding link.

According to one embodiment shown in FIGS. 5 and 6 , each pair ofsecondary jaws 80.1, 82.1, 80.2, 82.2 is designed to move in translationin a direction parallel to the face of the mold 56 on which the lateralextension 76.1, 76.2 held by the pair of secondary jaws 80.1, 82.1,80.2, 82.2 is to be positioned. Where there are first and second pairsof secondary jaws 80.1, 82.1, 80.2, 82.2, the first pair of secondaryjaws 80.1, 82.1, holding the right-hand lateral extension 76.1 of thefiber preform 72, 72′, moves in translation parallel to the first sideface 70.2 of the mold 56 and the second pair of secondary jaws 80.2,82.2, holding the left-hand lateral extension 76.2 of the fiber preform72, 72′, moves in translation parallel to the second side face 70.3 ofthe mold 56.

According to another embodiment shown in FIG. 7 , each pair of secondaryjaws 80.1, 82.1, 80.2, 82.2 is designed to move in translation in twodirections, a first direction parallel to the first or second side face70.2, 70.3 of the mold 56 and a second direction parallel to the bottomface 70.4 of the mold 56.

According to one arrangement, the tool has, for each pair of secondaryjaws, at least one sliding link 92 connecting the support 88 and thestructure 84 designed to allow the support 88 to move in translation atleast in a direction parallel to the first or second side face 70.2,70.3 of the mold 56.

Each pair of secondary jaws includes an upstream secondary jaw 80.1,80.2 and a downstream secondary jaw 82.1, 82.2. The concepts “upstream”and “downstream” refer to the direction of movement of the secondaryjaws, the upstream secondary jaw 80.1, 80.2 being located upstream ofthe downstream secondary jaw 82.1, 82.2. According to the example shownin FIGS. 5 and 6 , when the fiber preform 72, 72′ is positioned againstthe top face 70.1 of the mold 56, the upstream secondary jaw 80.1, 80.2is positioned above the right- or left-hand lateral extension 76.1, 76.2and the downstream secondary jaw 82.1, 82.2 is positioned below theright- or left-hand lateral extension 76.1, 76.2.

Each upstream secondary jaw 80.1, 80.2 comprises a first contact faceF80.1, F80.2 oriented towards the downstream secondary jaw 82.1, 82.2and a second contact face F80.1′, F80.2′ oriented towards the mold 56and substantially parallel to the face of the mold 56 against which thelateral extension 76.1, 76.2 held by the upstream and downstreamsecondary jaws 80.1, 82.1, 80.2, 82.2 is to be positioned. According toone arrangement, when the secondary jaws 80.1, 80.2, 82.1, 82.2 are inthe second position, the first contact faces F80.1, F80.2, F80.2, F82.2of the upstream and downstream secondary jaws are separated by adistance substantially equal to the thickness of the fiber preform 72,72′. For each upstream secondary jaw 80.1, 80.2, the second contact faceF80.1′, F80.2′ is spaced apart from the sections 52, 54 positioned onthe first or second side face 70.2, 70.3 of the mold 56 by a distancesubstantially equal to the thickness of the fiber preform 72, 72′.Therefore, when moving in translation, each upstream secondary jaw 80.1,80.2 and more specifically the second contact face F80.1′, F80.2′thereof, keeps the fiber preform 72, 72′ pressed against the sections52, 54 positioned on the first or second side face 70.2, 70.3 of themold 56.

According to a first layout, the fiber preform 72, 72′ is notpre-impregnated with resin. In this case, during the movement of thesecondary jaws 80.1, 80.2, 82.1, 82.2, the fiber preform 72, 72′ slidesbetween the first contact faces F80.1, F80.2, F80.2, F82.2 of theupstream and downstream secondary jaws and along the second contact faceF80.1′, F80.2′ of the upstream secondary jaws 80.1, 80.2.

According to a second layout, the fiber preform 72, 72′ ispre-impregnated with resin. According to one embodiment, at least onecontact face F78, F80.1, F80.2, F80.2, F82.2, F80.1′, F80.2′ of the jaws78, 80.1, 80.2, 82.1, 82.2 comprises a demolding film 94 limiting therisks of contamination of the fiber preform 72, 72′ and facilitating theremoval of the fiber preform where pre-impregnated with resin.

According to one arrangement, the contact face F78 of the main jaw 78has a demolding film 94.

Each downstream secondary jaw 82.1, 82.2 has at least one moving belt 96stretched between two pivoting rollers 98, 98′ on the first contact faceF82.1, F82.2 thereof. In operation, the moving belt 96 is in contactwith the fiber preform 72, 72′ and moves on the pivoting rollers 98,98′. This moving belt 96 can be a demolding film or coated with ademolding film.

According to a first layout, the movement of the moving belt 96 is idle.In this case, by moving at the same movement speed as the fiber preform72, 72′ between the upstream and downstream secondary jaws, the movingbelt 96 limits the friction between the fiber preform 72, 72′ and thedownstream secondary jaws 82.1, 82.2.

According to a second layout, the movement of the moving belt 96 iscontrolled, for example by setting at least one of the pivoting rollers98, 98′ to a given rotational speed. In this case, the moving belt 96regulates the tractive force exerted on the fiber preform 72, 72′.

Each upstream secondary jaw 80.1, 80.2 has at least one moving belt 100stretched between at least two pivoting rollers 102, 102′ on the firstand/or second contact face F80.1, F80.2, F80.1′, F80.2′ thereof.According to one layout, each upstream secondary jaw 80.1, 80.2 has asingle moving belt 100 stretched between at least three pivoting rollers102, 102′, 102″, the pivoting rollers being arranged such that themoving belt 100 moves on the first and second contact faces F80.1,F80.2, F80.1′, F80.2′. In operation, the moving belt 100 is in contactwith the fiber preform 72, 72′ and moves on the three pivoting rollers102, 102′, 102″.

According to a first layout, the movement of the moving belt 100 isidle. In this case, by moving at the same movement speed as the fiberpreform 72, 72′ between the upstream and downstream secondary jaws, themoving belt 100 limits the friction between the fiber preform 72, 72′and the upstream secondary jaws 80.1, 80.2.

According to a second layout, the movement of the moving belt 100 iscontrolled, for example by setting at least one of the pivoting rollers102, 102′, 102″ to a given rotational speed. In this case, the movingbelt 100 regulates the tractive force exerted on the fiber preform 72,72′.

The invention is not limited to the embodiments described above.

According to another embodiment illustrated in FIGS. 8 and 9 , theinvention can be used to manufacture a stiffened panel 104 comprising atleast one flange 106 folded through 90°. This stiffened panel 104comprises a main wall 108, such as a top or bottom panel or a front orrear spar for example, and the flange 106 forming an angle ofapproximately 90° with the main wall 108, the flange 106 being intendedto be connected with another wall, such as a top or bottom panel or afront or rear spar for example, so as to form a portion of a box.

The main wall 108 has stiffening members 50 on one of the faces thereof.

As before, this stiffened panel 104 is obtained from an outer skin madeof composite material and from a plurality of sections made of compositematerial each having a joining face in contact with the outer skin; themethod comprising a step of obtaining the sections, a step ofpositioning the sections on a face 70.1 of a mold 56, a step ofobtaining a flat fiber preform 72″ having a thickness substantiallyequal to the outer skin and a step of placing the fiber preform on thesections positioned on the first face 70.1 of the mold 56. The mold hasa second side face 70.2 shaped like the flange 106, forming an angle ofapproximately 90° with the first face 70.1.

The fiber preform 72″ includes a main portion 74 designed to bepositioned on the first face 70.1 of the mold 56 and at least onelateral extension 76.1 designed to be positioned on the second side face70.2 of the mold 56 after a forming step of the fiber preform 72′.

As before, for this forming step, the main portion 74 is held againstthe joining faces of the sections positioned on the first face 70.1 ofthe mold 56 by a main jaw 78 and the lateral extension 76.1 ispositioned between a pair of secondary jaws 80.1, 82.1 designed to movein translation in at least one direction parallel to the second face ofthe mold 56. On completion of the translational movement of the pair ofsecondary jaws 80.1, 82.1, the lateral extension 76.1 is pressed againstthe second side face 70.2 of the mold 56.

According to another embodiment, the stiffened panel 104′ includes twoflanges 106, 106′. These flanges 106, 106′ form an angle ofapproximately 90° with the main wall 108. According to one arrangement,the flanges 106, 106′ are folded in the same direction to obtain aU-shaped stiffened panel, or in opposite directions to obtain a Z-shapedstiffened panel 104′, as shown in FIG. 11 .

In order to obtain a flange 106′ folded away from the stiffening members50, the main jaw 78 has, in addition to the contact face F78, at leastone lateral contact face 78.1 shaped like the flange 106′ to beobtained. Where the stiffened panel 104′ includes a single flange 106′folded away from the stiffening members 50, the main jaw 78 has a singlelateral contact face 78.1. Where the stiffened panel includes twoflanges folded away from the stiffening members 50, the main jaw 78 hastwo opposing side contact faces.

To obtain a stiffened panel 104′ with two flanges 106, 106′, the flatfiber preform 72′″ comprises a main portion 74 intended to be positionedon the first face 70.1 of the mold 56 and the first and second lateralextensions 76.1, 76.2, on both sides of the main portion 74, the firstlateral extension 76.1 being folded against one of the side faces 70.2of the main mold 56 and the second lateral extension 76.2 being foldedagainst one of the lateral contact faces 78.1 of the main jaw 78 duringa forming step.

As before, for this forming step, the main portion 74 is held againstthe joining faces of the sections positioned on the first face 70.1 ofthe mold 56 by the main jaw 78.

According to a first procedure, during the forming step, each lateralextension 76.1, 76.2 is positioned between a pair of secondary jawsdesigned to move in translation in at least one direction parallel tothe side face 70.2 of the mold 56 or to the lateral contact face 78.1 ofthe main jaw 78.

The two pairs of secondary jaws can move in translation in the samedirection if the flanges 106, 106′ are folded in the same direction, orin opposite directions if the flanges 106, 106′ are folded in oppositedirections to obtain a Z-shaped stiffened panel 104′.

According to another simplified procedure shown in FIG. 10 , for thisforming step, the main portion 74 is held against the joining faces ofthe sections positioned on the first face 70.1 of the mold 56 by a mainjaw 78.

Furthermore, each lateral extension 76.1, 76.2 is folded against aforming surface, specifically either the side face 70.2 of the mold 56or the lateral contact face 78.1 of the main jaw 78, by means of anupstream secondary jaw 80.1, 82.1 that moves in translation in adirection of movement parallel to the forming surface by pushing thelateral extension 76.1, 76.2, the upstream secondary jaw 80.1, 82.1being positioned upstream of the lateral extension 76.1, 76.2 in thedirection of movement during the translational movement thereof. Thisupstream secondary jaw 80.1, 82.1 has a contact face oriented toward theforming surface and spaced apart from the forming surface by a distancesubstantially equal to the thickness of the flat fiber preform 72′″.

The faces of the upstream and/or downstream secondary jaws in contactwith the fiber preforms 72″, 72′″ may include a demolding film and/or amoving belt, as in the embodiment shown in FIG. 6 .

The manufacturing method according to the invention makes it possible toobtain a portion of a box structure comprising at least one stiffenedmain wall (such as a top or bottom panel or a front or rear spar)extended by at least one flange 106, 106′ and/or at least one stiffenedsecondary wall (such as a top or bottom panel or a front or rear spar),the portion of a box structure being obtained from an outer skin 60 madeof a composite material and a plurality of sections 52, 54 made ofcomposite material each having a joining face in contact with the outerskin 60. This method comprises:

a step of obtaining the sections 52, 54,

a step of positioning the sections 52, 54 on a mold 56 comprising atleast one first face 70.1 on which the sections 52, 54 are positioned,

a step of obtaining a flat fiber preform 72, 72′, 72″, 72′″ having athickness substantially equal to the outer skin 60,

a step of placing a central portion 74 of the fiber preform 72, 72′,72″, 72′″ on the sections 52, 54 positioned on the first face 70.1 ofthe mold 56, the fiber preform 72, 72′, 72″, 72′″ having at least onelateral extension 76.1, 76.2 extending the central portion 74,

a step of forming at least one lateral extension 76.1, 76.2 of the fiberpreform,

a step of applying at least one polymerization covering,

at least one polymerization step,

at least one demolding step.

During this forming step, the main portion 74 is held against thejoining faces of the sections positioned on the first face 70.1 of themold 56 by at least one main jaw 78. The contact face F78 of the mainjaw 78 may include a demolding film.

The fact that the central portion 74 of the fiber preform is pressedagainst the sections positioned on the first face 70.1 of the mold 56 bythe main jaw 78 enables a single lateral extension to be folded. Thus,the method according to the invention can be used to obtain stiffenedpanels with a single flange or a single stiffened secondary wall.According to another advantage, this optimizes the contact between thejoining faces of the sections and the fiber preform.

During the forming step, at least one lateral extension 76.1, 76.2 ofthe fiber preform 72, 72′, 72′″ is folded against a forming surface,substantially perpendicular to the first face 70.1 of the mold 56 usingat least one secondary jaw 80.1, 80.2, 82.1, 82.2 moving in translationparallel to the forming surface. According to the embodiments, theforming surface may be a side face 70.2, 70.3 of the mold 56, a contactface 78.1 of the main jaw 78 or the joining faces of the sectionspositioned on a side face 70.2, 70.3 of the mold 56. Folding at leastone lateral extension 76.1, 76.2 by positioning the lateral extensionbetween a pair of secondary jaws moving in translation parallel to theforming surface optimizes the deformation of the lateral extension 76.1,76.2 by preventing the lateral extension from becoming detached from theforming surface on completion of the forming step.

While at least one exemplary embodiment of the present invention(s) isdisclosed herein, it should be understood that modifications,substitutions and alternatives may be apparent to one of ordinary skillin the art and can be made without departing from the scope of thisdisclosure. This disclosure is intended to cover any adaptations orvariations of the exemplary embodiment(s). In addition, in thisdisclosure, the terms “comprise” or “comprising” do not exclude otherelements or steps, the terms “a” or “one” do not exclude a pluralnumber, and the term “or” means either or both. Furthermore,characteristics or steps which have been described may also be used incombination with other characteristics or steps and in any order unlessthe disclosure or context suggests otherwise. This disclosure herebyincorporates by reference the complete disclosure of any patent orapplication from which it claims benefit or priority.

1. A method for manufacturing at least one portion of a box structurecomprising at least one stiffened main wall extended by at least one ofat least one flange or at least one stiffened secondary wall, saidportion of the box structure being obtained from an outer skin made of acomposite material and from a plurality of sections made of a compositematerial, each of the plurality of sections having a joining face incontact with the outer skin, said method comprising: a step of obtainingthe sections, a step of positioning said sections on a mold comprisingat least a first face on which the sections are positioned, a step ofobtaining a flat fiber preform having a thickness substantially equal tothe outer skin, a step of placing a central portion of the fiber preformon the sections positioned on the first face of the mold, the fiberpreform having at least one lateral extension extending the centralportion, a step of forming the lateral extension, a step of placing atleast one polymerization covering, at least one polymerization step, andat least one demolding step; wherein during the forming step, the mainportion is kept pressed against the joining faces of the sectionspositioned on the first face of the mold by at least one main jaw, andwherein the lateral extension of the fiber preform is folded against aforming surface, substantially perpendicular to the first face of themold, by means of at least one secondary jaw configured to move intranslation parallel to the forming surface.
 2. The method as claimed inclaim 1, wherein during the forming step, the lateral extension of thefiber preform is held between a pair of secondary jaws configured tomove in translation in at least one direction parallel to the formingsurface.
 3. The method as claimed in claim 1, wherein the fiber preformincludes right- and left-hand lateral extensions positioned on bothsides of the main portion.
 4. The method as claimed in claim 1, whereinthe forming surface corresponds to joining faces of sections positionedon a side face of the mold.
 5. A method for manufacturing a centralwingbox comprising a top panel, a bottom panel, a front spar and a rearspar, wherein the central wingbox comprises: a first portion comprisingthe top panel, the front and rear spars, and the first and secondflanges, the first flange being connected to the front spar,approximately perpendicular to said front spar and extending said frontspar in a direction opposite the rear spar, the second flange beingconnected to the rear spar, approximately perpendicular to said rearspar and extending said rear spar in a direction opposite the frontspar, said first portion being obtained using the manufacturing methodas claimed in claim 1, a second portion comprising a stiffened panelshaped like the bottom panel and including first and second extensionsarranged on both sides of the bottom panel, the first extension beingconnected to the first flange, the second extension being connected tothe second flange.
 6. A central wingbox obtained using the manufacturingmethod as claimed in claim
 5. 7. A forming tool for implementing themanufacturing method as claimed in claim 1 for at least one portion of abox structure comprising at least one stiffened main wall extended by atleast one of at least one flange or at least one stiffened secondarywall, wherein the forming tool comprises: a mold having at least a firstface shaped like the stiffened main wall and configured to bearsections, at least one main jaw comprising a contact face substantiallyparallel to the first face of the mold, configured to hold a mainportion of a fiber preform pressed against sections positioned on thefirst face of the mold, at least one secondary jaw configured to fold alateral extension of the fiber preform against a forming surface and tomove in at least one direction parallel to the forming surface.
 8. Aforming tool as claimed in claim 7, wherein the forming tool comprisesat least one pair of upstream and downstream secondary jaws eachconfigured to hold a lateral extension of the fiber preform and to movein a direction parallel to the forming surface.
 9. The forming tool asclaimed in claim 8, wherein each upstream and downstream secondary jawcomprises a first contact face, the first contact faces of the upstreamand downstream secondary jaws, being configured to be arranged on bothsides of the fiber preform, substantially parallel to each other foreach pair and perpendicular to a face of the mold against which thelateral extension held by the upstream and downstream secondary jaws isto be positioned.
 10. The tool as claimed in claim 9, wherein eachupstream secondary jaw comprises a second contact face oriented towardsthe mold, substantially parallel to the face of the mold against whichthe lateral extension held by the upstream and downstream secondary jawsis to be positioned, in operation the second contact face being spacedapart from the sections positioned on said face of the mold by adistance substantially equal to the thickness of the fiber preform. 11.The forming tool as claimed in claim 10, wherein each downstreamsecondary jaw has at least one moving belt on the first contact facethereof.
 12. The forming tool as claimed in claim 10, wherein eachupstream secondary jaw has at least one moving belt on at least one ofthe first or second contact face thereof.
 13. The forming tool asclaimed in claim 12, wherein each upstream secondary jaw has a movingbelt stretched between at least three pivoting rollers arranged suchthat the moving belt moves on the first and second contact faces. 14.The forming tool as claimed in claim 8, wherein the tool comprises afirst pair of secondary jaws configured to cooperate with a right-handlateral extension of the fiber preform and a second pair of secondaryjaws configured to cooperate with a left-hand lateral extension of thefiber preform.